As is known in the art, computer systems generally include a central processing unit (CPU), a memory subsystem, and a data storage subsystem. According to a network or enterprise model of the computer system, the data storage system associated with or in addition to a local computer system, may include a large number of independent storage devices, typically disks housed in a single enclosure or cabinet. This array of storage devices is typically connected to several computers or host processors over a network or via dedicated cabling. Such a model allows for the centralization of data that is available to many users but creates a critical hub for operations.
Recently, disk redundancy has evolved as an alternative or complement to historical backups of the information stored on this critical hub. Generally speaking, in a redundant system having at least two storage devices, such as disk storage devices, data is copied or replicated and stored in more than one place. This allows the data to be recovered if one storage device becomes disabled.
In a basic approach, a first disk storage device stores the data and a second disk storage device stores a mirror image of that data. Whenever a data transfer is made to the first disk storage device, the data is also transferred to the second disk storage device. Typically, separate controllers and paths interconnect the two disk storage devices to the remainder of the computer system.
The concept of disk redundancy has been extended to environments wherein disks targeted for copying and storage of information are located remote to the source or primary disk. Remote redundancy provides further protection for data integrity because if a disaster or other unfortunate event renders the primary data unusable the remotely located target is much more likely to be unaffected than locally located disks.
Such redundancy may also be useful for reasons other than data backup. Uses include creating test environments with production data, or even creating alternative production sites for use while the primary production site is not available. Redundancy or mirroring on a global basis would be a boon for business. Some limited global data replicating has been performed globally using the internet. But there are serious impediments to employing such techniques on a normal basis.
One limit is the amount of bandwidth capacity (hereafter bandwidth), i.e., the amount of data that can be passed along a communications channel in a given period of time required for such a task. It is exceedingly expensive. But not allocating enough would impair the operation probably to the point of failure. On the other hand, allocating too much, particularly for an excessive amount of time would create economic waste, which by itself might make the operation to expensive to undertake on a regular basis. Yet the availability of networks for regular disk redundancy is one of the normal expectations in a non-internet environment and a critical linchpin for justifying costs of data storage hardware and software.
What is needed is a tool that allows for adequate and efficient management of network resources, such as bandwidth required for data replication over the internet and while allowing for good performance throughput of the replication process.